The present invention is directed to novel cinnamide derivatives which are modulators of KCNQ potassium channels and are therefore useful in treating disorders responsive to the modulation of the potassium channels. The present invention also provides a method of treatment with the novel cinnamide derivatives and to pharmaceutical compositions thereof.
Potassium (K+) channels are considered to be the most diverse class of ion channels and have several critical roles in cell function. This has been demonstrated in neurons where K+ channels are responsible, in part, for determining cell excitability by contributing to membrane repolarization following depolarization, resting membrane potential, and regulation of neurotransmitter release. The M-current has long been described, by electrophysiology recording methods and by pharmacology, as a dominant conductance in controlling neuronal excitability. Pharmacological activation or suppression of M-currents by small molecules could have profound effects in controlling neuronal excitability. Recently, Wang et al., Science, 282:1890-1893, (1998) reported that co-assembly of the KCNQ2 and KCNQ3 potassium channels underlies the native M-current in neurons.
Activation or opening of the KCNQ channel(s), particularly the KCNQ2 or KCNQ2/3 channel(s), mutated or wild type, may prove to be beneficial in increasing hyperpolarization of neurons, thereby resulting in protection from abnormal synchronous firing during a migraine attack. The present invention provides a solution to the problem of abnormal synchronous firing of neurons related to migraine headache by demonstrating that modulators, preferably openers, of KCNQ potassium channels increases hyperpolarization of neurons which protects against abnormal synchronous neuron firing involved in migraine attacks.
Although the symptom pattern varies among migraine sufferers, the severity of migraine pain justifies a need for vigorous, yet safe and effective, treatments and therapies for the great majority of cases. Needed in the art are agents that can be used to combat and relieve migraine (and diseases similar to and mechanistically related to migraine), and even prevent the recurrence of migraine. Also needed are anti-migraine agents which are effective in the treatment of acute migraine, as well as in the prodrome phase of a migraine attack. Thus, a clear goal in the art is to discover new, safe, nontoxic and effective anti-migraine compounds for use as drugs, and in anti-migraine compositions and treatments.
Because migraine afflicts a large percentage of the population, there is a need to discover compounds and agents that are useful in therapeutics and treatments, and as components of pharmaceutical compositions, for reducing, ameliorating, or alleviating the pain and discomfort of migraine headache and other symptoms of migraine. The present invention satisfies such a need by providing compounds that function as openers of the KCNQ family of potassium channel proteins to serve as anti-migraine agents or drugs and to comprise compositions to treat migraine, as described herein.
A broad range of cinnamide compounds are known and new compounds continue to be reported with a broad range of utility. Some of these compounds can be found in the disclosures of WO 00/07993 published Feb. 17, 2000, EP 810220A1, published Dec. 3, 1997, U.S. Pat. No. 4,927,838 issued May 22, 1990 to Guthrie, et al., U.S. Pat. No. 6,046,239 issued Apr. 4, 2000 to Lennox, et al., WO 00.42013, published Jul. 20, 2000, WO 01/10381 published Feb. 15, 2001, WO 01/10380 published Feb. 15, 2001, JP45-14291 published May 21, 1970, and JP2-138159 published May 28, 1990. The compounds described in these patents are distinct from those of the present invention.
The present invention provides novel cinnamides and related derivatives having the general Formula I: 
wherein R, R1, R2, R3, R4, R5, R6, R7, R8 and R9 are as defined below, or a nontoxic pharmaceutically acceptable salt, solvate or hydrate thereof which are openers or activators of KCNQ potassium channels. The present invention also provides pharmaceutical compositions comprising said cinnamides and to the method of treatment of disorders sensitive to KCNQ potassium channel opening activity such as migraine or a migraine attack, bipolar disorders, epilepsy, acute and chronic pain and anxiety.